Firstly could someone confirm it is a CuO rectifier
http://home.graffiti.net/diverse:gra...et/CuO_rec.jpg
steel bolt mount is horizontal,
from a mid 30s Avo, "Mark 1" valve/tube tester, discs about 3/4 inch
diameter, gives only about 4V dc.
Assuming functional replacement with a 1N4007, what value of sag resistor?
Is the functional part just the 6 central discs and the outer discs are just
insulators/strain relief, they seem a bit more than that ?